(1) Field of the Invention
The present invention relates to a linear compressor for reciprocating a piston in a cylinder by a linear motor to suck, compress and discharge gas.
(2) Description of the Prior Art
In refrigeration cycles, HCFC refrigerants, such as R22, are stable compounds and decompose the ozone layer. In recent years, HFC refrigerants have begun to be utilized as alternative refrigerants of HCFCs, but these HFC refrigerants have the nature for facilitating global warming. Therefore, a study is started to employ natural refrigerants such as HC refrigerants which do not decompose the ozone layer or largely affect global warming. For example, since an HC refrigerant is flammable, it is necessary to prevent explosion or ignition so as to ensure safety. For this purpose, it is required to reduce the amount of refrigerant to be used to as small as possible. The HC refrigerant itself does not have lubricity and is easily melted into a lubricant. For these reasons, when an HC refrigerant is used, an oilless or oil-poor compressor is required. On the other hand, a linear compressors, in which a load applied in a direction perpendicular to an axis of its piston is small and a sliding surface pressure is small is known as a compressor which can easily realize oilless conditions as compared with a reciprocal type compressor, a rotary compressor or a scroll compressor.
However, in this linear compressor, propagation of vibration caused by reciprocating motion of the piston is a big problem. A system for elastically supporting a compressing mechanism portion in a hermetic vessel to suppress vibration is conventionally employed in many cases, but it is difficult to sufficiently suppress the vibration. Means for lowering the vibration by opposing two pistons to each other is used, but a very complicated design is required.
The present invention has been accomplished in view of the above circumstances, and it is an object of the invention to provide a linear compressor in which a driving spring and an elastic supporting member for supporting a compressing mechanism portion are disposed such that a piston and the compressing mechanism portion move in opposed phases so that vibration of a hermetic vessel is canceled out.
To achieve the above object, according to a first aspect of the present invention, there is provided a linear compressor comprising a hermetic vessel having a compressing mechanism portion and a linear motor therein, wherein the compressing mechanism portion comprises a cylinder and a piston which reciprocates in the cylinder, the linear motor comprises a moving member which provides the piston with reciprocating driving force and a stator which is fixed to the cylinder and which forms a reciprocation path for the moving member, the compressing mechanism portion and the linear motor are classified into a piston-side mechanism member and a cylinder-side mechanism member, the piston-side mechanism member includes the piston, the moving member and another mechanism member which is movable together with the piston and the moving member, the cylinder-side mechanism member includes the cylinder, the stator and another mechanism member fixed to the cylinder or the stator, the cylinder-side mechanism member is elastically supported in the hermetic vessel by a first elastic member, and a reciprocating force in the axial direction is given to the piston-side mechanism member by a second elastic member whose one end is supported by the hermetic vessel.
According to a second aspect of the invention, in the linear compressor of the first aspect, the first elastic member and the second elastic member respectively comprise spring members, and the first elastic member and the second elastic member are disposed such that their vibrating directions are the same.
According to a third aspect of the invention, in the linear compressor of the second aspect, a relation of substantially Mpxc3x97k1=Mmxc3x97k2 is established, in which mass of the piston-side mechanism member is defined as Mp, mass of the cylinder-side mechanism member is defined as Mm, the spring constant of the first elastic member is defined as k1, and the spring constant of the second elastic member is defined as k2.
According to a fourth aspect of the invention, in the linear compressor of the second aspect, the first elastic member comprises a plurality of plate-like leaf springs.
According to a fifth aspect of the invention, in the linear compressor of the fourth aspect, the first elastic member comprises a combination of a pair of substantially C-shaped leaf springs, the second elastic member is a coil spring, and the second elastic member is disposed in a central space of the first elastic member.
According to a sixth aspect of the invention, in the linear compressor of the second aspect, the first elastic member is a non-linear spring having a linear spring stiffness up to a certain displacement and the spring stiffness is abruptly increased thereafter.
According to a seventh aspect of the invention, in the linear compressor of the sixth aspect, the first elastic member is a coil spring.
According to an eighth second aspect of the invention, in the linear compressor of the sixth aspect, the first elastic member is a laminated leaf spring.
According to a ninth aspect of the invention, in the linear compressor of any one of the first to eighth aspect, the linear compressor is operated using refrigerant mainly comprising carbon dioxide.
According to the first aspect, the cylinder-side mechanism member is elastically supported in the hermetic vessel by the first elastic member, and a reciprocating force in the axial direction is given to the piston-side mechanism member by a second elastic member whose one end is supported by the hermetic vessel. With this structure, since the amplitude of the piston-side mechanism member and the amplitude of the cylinder-side mechanism member are different in phase, vibration of the hermetic vessel becomes small.
According to the second aspect, in the linear compressor of the first aspect, the first elastic member and the second elastic member respectively comprise spring members, and the first elastic member and the second elastic member are disposed such that their vibrating directions are the parallel. With this structure, the amplitude of the piston-side mechanism member and the amplitude of the cylinder-side mechanism member becomes opposite in phase, and vibration transmitted to the hermetic vessel is canceled out. Therefore, a linear compressor having smaller vibration as compared with the first aspect can be obtained.
According to the third aspect, in the linear compressor of the second aspect, a relation of substantially Mpxc3x97k1=Mmxc3x97k2 is established, in which mass of the piston-side mechanism member is defined as Mp, mass of the cylinder-side mechanism member is defined as Mm, spring constant of the first elastic member is defined as k1, and spring constant of the second elastic member is defined as k2. With this structure, the vibration displacement of the hermetic vessel becomes substantially 0, and a linear compressor having almost no vibration can be obtained.
According to the fourth aspect, in the linear compressor of the second aspect, the first elastic member comprises a plurality of plate-like leaf springs. Since the leaf spring is strong against lateral load as compared with a coil spring, high reliability can be obtained even if disturbance force is applied to the compressor.
According to the fifth aspect, in the linear compressor of the fourth aspect, the first elastic member comprises a combination of a pair of substantially C-shaped leaf springs, the second elastic member is a coil spring, and the second elastic member is disposed in a central space of the first elastic member. With this structure, the compressor can be reduced in size in its longitudinal direction.
According to the sixth aspect, in the linear compressor of the second aspect, the first elastic member is a non-linear spring having a linear spring stiffness up to a certain displacement and the spring stiffness is abruptly increased thereafter. With this structure, even if extremely great disturbance force which coincides with resonance frequency of the mechanism member in the hermetic vessel is applied, if the first elastic member reaches a certain displacement, the resonance frequency of the mechanism member is deviated toward a higher value. Therefore, resonance disruption of the mechanism member is avoided.
According to the seventh aspect, in the linear compressor of the sixth aspect, the first elastic member is a coil spring. Since the non-linear spring comprises a coil spring which is easily produced, the spring can be produced with relatively low cost.
According to the eighth aspect, in the linear compressor of the sixth aspect, the first elastic member is a laminated leaf spring. Since the non-linear spring comprises the laminated leaf spring which is compact in its axial direction, the compressor can be reduced in size in its longitudinal direction.
According to the ninth aspect, in the linear compressor of any one of the first to eight aspects, refrigerant mainly comprising carbon dioxide is used. In addition to the effects of the first to eighth aspects, the linear compressor has smaller load in a direction perpendicular to an axis of its piston and has small sliding surface pressure. Thus, if CO2 refrigerant in which it is difficult to lubricate with high different pressure refrigerant is used, efficiency is extremely excellent as compared with another compressor, and high reliability can be obtained.